Coded data decoder



June 1 INF FIG. I 3

A. B. JACOBSEN 3,093,798

CODED DATA DECODER Original Filed Sept. 19, 1945 UT 12 I8) 22-? OUTPUTTRANSMITTER i6 17 RECElVER m m 19 Zl 0005a DEGODER TIME Zinnentor Anreal B. Jacobsen (Ittornegs United StatesPatent Oficc 4 w 3,093,798 tedJune 11, 1963 DATA DECODER Andrew B. Jacobsen, Somerville, Mass,asslgnor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Original application Sept. 19,1945, Ser. No. 617,365, now Patent No. 2,772,399, dated Nov. 27, 1956.Divided and this application Feb. 10, 1954, Ser. No. 410,744

8 Claims. (Cl. 328-67) CODED This invention relates to coding apparatusand is a division of my copending application, Serial No. 617,365, filedSeptember 19, 1945 for a coded data transmission system and moreparticularly to a transmission system, now U.S. Patent No. 2,772,399 ofNovember 27, 1956 employing a coder for coding a pulse of electricalenergy into a plurality of code pulses with predetermined time spacings.

Electromagnetic energy pulse transmission is now wellknown to the art;numerous radiant energy echo ranging devices employ it as a basic Recentdevelopments in this field have included such radiant energy echoranging devices carried aboard an aircraft, the information received bythe aircraft from these devices being conveyed by supplementary relaying,rneans to a ship or land station in order to increase the detectionrange of a ship or land station. Such a pulsed echo ranging device andrelaying system is described more fully in patent application SerialNumber 592,794, for a Synchronizer for Indicators filed May 9, 1945 byStanley N. Van Voorhis, now U.S. Patent No. 2,698,931 of January 4,1955. In relaying such pulsed information it is important that militarysecurity be preserved and also that there be no confusion as a result ofinterference from a spurious source, such as atmospheric noise or otherecho ranging systems.

Accordingly, it is one object of this invention to provide a means forrelaying and receiving information carried in the form ofelectromagnetic energy which will preclude the possibility of confusioncaused by interference from spurious sources. 1

Another object is to provide means for relaying and receivinginformation carried in the form of electromagnetic energy which Willinsure military security of this information. 1 A further object is toprovide a means for coding a pulse of electrical energy into a pluralityof code pulses with predetermined time spacings, transmitting these codepulses in the form of electromagnetic energy, and receiving andconverting them back into one pulse of electrical energy.

Still another object is to provide a means for coding a pulse ofelectrical energy into a plurality of code pulses with predeterminedtime spacings.

Other and further objects will appear in the course of the followingdescription when taken with the accompanying drawings in which:

FIG. 1 illustrates in block form a system this invention;

FIG. 2 illustrates one embodiment of this invention;

' FIG. 3 shows the pulse waveforms associated with FIG. 2, plotted as afunction of time;

FIG. 4 illustrates an alternative embodiment of this in vention; and,

FIG. 5 shows the pulse waveforms associated with FIG. 4, plotted as afunction of time.

In FIG. 1 any desired information in the formof single pulses ofelectrical energy is fed into input 11 of a conventional pulsetransmitter 12, whose construction and design are well-known to thoseslcilled in the art and hence need not be given here. At any convenientpoint embodying principle of their operation.

in transmitter 112 is connected input 13 of coder 14, which will be morefully described hereafter in this specification. The purpose of thiscoder is to code each pulse received at its input into a plurality orseries of code pulses separated by predetermined time spacings. Output15 of coder .14 then feeds these code pulses into transrnitter 12, andafter further amplification and modulation these code pulses areradiated into space in the form of electromagnetic energy bytransmitting antenna 16. These same code pulses are then picked up byreceiving antenna 17 and fed into a conventional pulse receiver 18,whose construction and design are well-known to those skilled in the artand hence need not be given here. Input 19 of decoder 20 is connected atany convenient point in receiver 18. The purpose of the decoder is todecode the series of code pulses into a single pulse which then givesthe original information or data fed into input 11 of transmitter 12.Such decoders are described in copending application, Serial Number617,151, filed September '18, 1945, now U.S. Patent No. 2,706,810 issuedApril 19, 1955 for a Coded Data Decoder. Decoder output 21 is then fedback into receiver 18 for further amplification of this single pulse andthe aforementioned original data is ultimately available at receiveroutput 22.

In FIG. 2 a coder is shown which comprises two sections of delay line 25and 26, connected in series. Open end 29 of delay line 25 will bedesignated as the input and open end 30- of delay line 26 and will bedesignated as the output. Physically, each delay line is composed of athin inductive coil surrounded by a cylindrical outer conductor which isrepresented in FIG. 2 by straight lines 27 and 28 under the coilsymbols. Variable resistor 31 is connected between outer conductors 27and 28, variable resistor 32 is connected between outer conductor 27 andground, and resistor 33 is connected between outer conductor 28 andoutput 30. Any pulse applied at input 29 will then be delayed aspecified period of time determined by the construction of delay lines25 and 26 before appearing at output 30.

For purposes of illustration assume that a single pulse of onemicrosecond duration is applied to input 29. This pulse, which isrepresented by waveform 40 in FIG. 3, is instantaneously capacitycoupled to outer conductor 27, producing a voltage drop across variableresistor 32 and simultaneously appearing at output 30, since variableresistor 31 and resistor 33 form an undelayed conducting path. Thisinitial pulse produced at output 30 is represented by waveform 41, whichis of lesser magnitude than waveform 40 due to the voltage drop in theresistors. Assuming that delay line 25 produces a delay of amicroseconds, a microseconds later the original pulse enters the inputend of delay line 26 and similarly is capacity coupled to its outerconductor 23, producing a voltage drop across variable resistors 31 and32, and instantly appears at output 30, as represented by "waveform 42.Again, waveform 42 is of lesser magnitude than waveform 40 due to thevoltage drop in the resistors and also the attenuation introduced bydelay line 25. Assuming that delay line 26' introduces a delay of bmicroseconds, b microseconds later the original pulse reaches output 30,as represented by waveform 43, whose decreased magnitude is due to theattenuation of delay lines 25 and 26. By the proper choice of relativeimpedance values for resistor 33 and variable resistors 31 and 32,waveforms 41, 42, and 43 and their corresponding pulses can be andpreferably are in operation made equal in magnitude, though of coursesmaller than waveform 40 and the corresponding original pulse. Theimpedance of resistor 33 is made equal in magnitude to thecharacteristic impedance of delay line 26 and the maximum impedance ofresistor 31 is made from one-fourth to one-half this char acteristicimpedance. Further, resistors 31 and 32 are made variable to facilitatethe proper adjustment of the magnitudes of waveforms 41, 42, and 43 andtheir corresponding pulses. Therefore, the final result is that in placeof the original pulse there is now a series of three pulses: the initialpulse followed by its delayed image a microseconds later, which in turnis followed by its delayed image b. microseconds later. The total timedelay introduced by delay lines 25 and 26 in series is c microseconds,where a plus b equals '0.

In FIG. 4 is shown an alternative coder which includes a delay'line 50of construction similar to that described above, its outer conductorbeing represented by straight line 51. This embodiment employs fourvacuum tubes 52, 53, 54, and 55 of the conventional triode type, eachhaving a grid, plate, and cathode. Oathode heaters and heater circuits,being well-known to those skilled in the art, are omitted here for thesake of simplification of the diagram. All these tubes are used ascathode followers, and the points at which they are connected to delayline 50 are determined by the coding desired. Tubes 52 and 53 are usedas input tubes and tubes 54 and 55 as output tubes. In this embodimentfor the coding hereafter described tubes 52 and 54 are connected toinput 56 of delay line 50, tube 55 is connected to output 57 of delayline 50, and tube 53 is connected to some intermediate tap or point 58on delay line 50. A pulse input 59 is connected to grid 60 of tube 52,and to this same grid is connected one end of grid resistor 61. To theother end of grid resistor 61 is connected a suitable source of negativebias voltage at terminal 62. Plate 63 is connected to a source of platevoltage at terminal 64 and cathode 66 is connected to input 56 of delayline 50' and to one end of a resistor 67, whose other end is connectedto ground and whose ohmic value is equal to the characteristic impedanceof delay line 50. A second pulse input 68 is connected to grid 69 oftube 53 and to one end of grid resistor 70, whose other end is connectedto a suitable source of negative bias voltage at terminal 71. Plate 72is connected to a source of plate voltage at terminal 73 and cathode 75is connected to point 58 on delay line 50 as previously mentioned. Outerconductor 51 of delay line 50 is grounded as is one end of resistor 76,whose other end is connected to output 57 and whose ohmic value is equalto the characteristic impedance of delay line '50. Input 56 is connectedto grid 77 of tube 54 and output 57 is connected to grid 78 of tube 55.Plates 79 and 80 are connected to suitable sources of plate voltage atterminals 81 and 82 respectively and cathodes 85 and 86 are connectedtogether and to one end of cathode resistor 87, whose other end isgrounded. This common cathode junction point also serves as output 88 ofthe coder circuit.

Referring now to FIG. also, assume first that a single pulse of onemicrosecond duration is applied to input 59 of tube 52. This originalapplied pulse is represented by waveform '90. Due to the circuitpreviously described, this pulse will instantaneously appear at output88, although reduced in magnitude due to the cathode follower action oftubes 52 and 54 in the circuit. This initial pulse at output 88 isrepresented by waveform 91. Assuming that delay line 50 introduces adelay of d microseconds,-d microseconds later a second pulse will passthrough tube 55 and appear at output 88, as represented by waveform 9 2.The magnitude of this pulse will also be less than that of the originalapplied pulse due to the cathode follower action of tubes 52 and 55 andthe attenuation of delay line 50. Thus a single pulse has been codedinto two pulses delayed one from the other by a predetermined spacing d.

Next assume that the original pulse is applied not to input 59, butinstead to input 68, and that delay line 50 introduces a delay of emicroseconds between points 56 and 58 and microseconds between points 57and 58. From this it is also apparent that e plus equals d. Tracingthrough the circuit, an original pulse applied to input 68 and againrepresented by Waveform 90 would result in a pulse delayed fmicroseconds at output 88, as represented by waveform 93, and a pulsedelayed e microseconds at output 88, as represented by waveform 94.Again the magnitudes of these waveforms 93 and 94 and theircorresponding pulses are less than that of the original pulse and itswaveform 90 due to the cathode follower action of tubes 53 and 55 andthe attenuation introduced by delay line 50 between points 57 and 58 andthe cathode follower action of tubes 53 land 54 and the attenuationintroduced by delay line 50 between points 56 and 58 respectively.

7 Finally, if the same original pulse represented by Waveform 90 isapplied to inputs 59 and 68 simultaneously the resultant at output 88will be as shown in the bottom line of waveforms in FIG 5, includingwaveforms '91, 93, 94, and 92, spaced as shown. Y

Thus it is obvious that this second embodiment provides a very flexiblecoding means, 'since by providing various taps on delay line 50 andvarying the inputs to the various input tubes and the connections fromthe input and output tubes to these various taps a multiplicity of codesmay 'be simply and easily obtained. Also, of course, additional similarinput and output tubes can be added to obtain an even greater variety ofcodes.

it is to be understood that while the operation of the above embodimentsof t "s invention has been described with reference to a single inputpulse, the embodiments are operable with a plurality of successivepulses. Further, while specific embodiments have been described asrequired by the Patent Statutes, the principles of this invention are ofmuch broader scope. Numerous additional specific applications, as, forexample, employing multivibrators, will occur to those skilled in theart and no attempt has been made to exhaust such possibilities. Thescope of the invention is defined in the following claims.

What is claimed is:

1. In a transmission system, a coder comprising a delay line, a resistorconnected between one end of said delay line and ground, a secondresistor connected between the other endof said delay line and ground,each of said resistors having an impedance equal to the characteristicimpedance of said delay line, a cathode follower circuit including atriode vacuum tube on whose grid may be impressed a pulse input andwhose cathode is connected to one end of said delay line, a secondcathode follower circuit including a triode vacuum tube whose grid iscon nected to the same end of said delay line, a third cathode followercircuit including a triode vacuum tube whose grid is connected to theother end of said delay line, a common cathode resistor connectedbetween ground and the cathodes of said vacuum tubes included in saidsecond and third cathode follower circuits, said cathodes beingconnected together and also to the output terminal of the coder, and afourth cathode follower circuit including a triode vacuum tube on whosegrid may also be impressed a pulse input and whose cathode is connectedto any desired tap on said delay line.

2. Apparatus for producing predetermined sequential time-spaced outputpulses for each input pulse comprising, a delay line having input tapsspaced asymetrically with respect to its transverse axis of electricalsymmetry, the ends of said delay line being terminated by resistors,each of said terminating resistors having an ohmic value equal to thecharacteristic impedance of said delay line, a pair of electron tubes, aresistor common to the cathodes of said electron tubes, the inputcircuit of each of said electron tubes being coupled across a dilferentone of said terminating resistors, and means for taking the outputacross the said common resistor.

3. Apparatus for producing a train of time spaced output pulses from aninput pulse comprising, in combination, a delay line, said delay lineterminating at each end in its characteristic impedance, means forapplying an input pulse simultaneously to two spaced points along saiddelay line, said points being asymmetrically spaced with respect to thetransverse axis of electrical symmetry of said delay line and means forcombining the pulses appearing across said characteristic impedancesthereby to produce a train of time spaced output pulses.

4. In a system as defined in claim 3 wherein one of said spaced pointsis located at one end of said delay line whereby one of the pulses inthe train coincides in time with said input pulse.

5. In a system as defined in claim 3 wherein said means for applyingsaid input pulse includes a first pair of cathode follower stages, oneof said stages having as its cathode load resistor one of saidcharacteristic impedances.

6. In a system as defined in claim 3 wherein said means for applyingsaid input pulse includes a first pair of cathode follower stages, oneof which stages has as its cathode load resistor one of saidcharacteristic impedances and the other of which has as its cathode loadresistor a portion of said delay line and the other of saidcharacteristic impedances.

7. In a system as defined in claim 6 wherein said means for combiningsaid pulses appearing across both of said characteristic impedancesincludes a second pair of cathode follower stages, said stages havingtheir input circuits connected to difierent ones of said characteristicimpedances and a single resistor serving as the cathode load resistorfor said second pair of cathode followers whereby said train of timespaced output pulses occurs across said single resistor.

8. A wave signal coder for translating each signal pulse into apredetermined number of time spaced output pulses comprising, a delayline having first and second asymmetrically spaced input taps, [aterminating resistor at each end of said delay line, each resistorhaving a magnitude equal to the characteristic impedance of said delayline, means for applying an input pulse simultaneously to both of saidspaced input taps, means for combining the pulses appearing across saidterminating resistors, said combining means including a pair of electrontubes having a common cathode resistor and each end of said delay linebeing coupled to the control grid of a different one of said electrontubes.

References Cited in the file of this patent UNITED STATES PATENTS

3. APPARATUS FOR PRODUCING A TRAIN OF TIME SPACED OUTPUT PULSES FROM ANINPUT PULSE COMPRISING, IN COMBINATION, A DELAY LINE, SAID DELAY LINETERMINATING AT EACH END IN ITS CHARACTERISTIC IMPEDANCE, MEANS FORAPPLYING AN INPUT PULSE SIMULTANEOUSLY TO TWO SPACED POINTS ALONG SAIDDELAY LINE, SAID POINTS BEING ASYMMETRICALLY SPACED WITH RESPECT TO THETRANSVERSE AXIS OF ELECTRICAL SYMMETRY OF SAID DELAY LINE AND MEANS FORCOMBINING THE PULSES APPEARING ACROSS SAID CHARACTERISTIC IMPEDANCESTHEREBY TO PRODUCE A TRAIN OF TIME SPACED OUTPUT PULSES.